Copper is an essential trace nutrient critical to human health. As a prominent cofactor in metalloproteins, it is required to support many fundamental biological functions, including respiration, superoxide detoxification, degradation of amines, and the mobilization and uptake of iron. Cellular copper levels are tightly controlled through a complex network of membrane transporters, chaperone proteins, ligands, and transcription factors. If placed in the wrong environment, copper has the ability to catalyze the production of hydroxyl radicals and other reactive oxygen species, a common deleterious mechanism that has profound implications in neuro- degenerative diseases (ALS and Alzheimer's disease) and diseases associated with copper mistrafficking (Menkes and Wilson's disease). As the pathological conditions are often caused by the toxicity of mislocalized copper rather than the failure to deliver copper to cuproenzymes, a detailed knowledge of the copper interactions within the cellular proteome is of fundamental importance. The goal of this grant application is to develop molecular tools that will allow researchers to dissect and discover new copper trafficking pathways, both under normal physiological conditions and their alterations in diseases associated with copper dyshomeostasis. In a wider context, the proposed tools are expected to be of critical importance for the long- term development of novel diagnostic and therapeutic methods to combat copper related human diseases.